Method for the explosive deformation of material and products manufactured accordingto this method



United States Patent 3 228 757 METHOD FOR THE EXPiGSIVE DEFORMATION 0F MATERIAL AND PRODUCTS MANUFAC- TURED ACCORDING TO THIS METHOD Cornelis A. Verbraak, Delft, Netherlands, assignor to Nederlandse OrganiSatie voor Toegepast-Natuurwetenschappelijlr Onderzoek ten Behoene van Nifiverlierd, Handel en Verkeer, The Hague, Netherlands, a corporation of the Netherlands No Drawing. Filed Mar. 11, 1963, Ser. No. 264,064 Claims priority, application Great Britain, Mar. 19, 1962, 10,450/ 62 6 Claims. (Cl. 29-180) This invention relates to a method for the explosive deformation of material having a mainly cubically facecentered crystal lattice and to products manufactured according to this method.

' In the production of large and not easily formed articles, explosive deformation, or the deformation of the material with the aid of shock-waves, presents considerable advantages over conventional deformation methods such as pressing or deep-drawing, since it requires less investment, less time, and affords greater deformation possibilities.

In all of these conventional deformation methods such as deep-drawing, pressing or stamping, what is aimed at is as isotropic as possible a starting material, because thereby the best result is obtained. However, it has been found that such an isotropic material after explosive deformation shows a depreciation of certain properties.

Materials having a considerable resistance against corrosion for instance, after having been explosively deformed into products, show a considerably decreased resistance to stress corrosion, which decrease is caused by the occurrence of mechanical twin formation.

The fact is that mechanical twin formation gives rise to extremely high stress concentrations in the grains and on the grain boundaries and it is to this high stress that stress corrosion is due. In order to compensate this depreciation of the properties as much as possible, a suitable heat treatment may be applied after the explosive deformation, but this treatment increases the costs and moreover, by its probable deformation, if affects the possibility of achieving a high accuracy of shape, which accuracy is indeed one of the advantages of explosive deformation.

It is the object of the present invention to produce a method of explosive deformation, in which the desired properties of the material are as far as possible preserved, in the sense that the properties of the products manufactured by means of explosive deformation are not inferior to and if possible better than those of products made according to some other method.

If, according to this invention, the shock-wave of the explosion is directed along or substantially parallel to the 110 direction of the crystals of a material having a cubically face-centered lattice and a texture, it appears that no mechanical twin formation occurs. The suppression of mechanical twin formation is an essential condition for the prevention of a decrease in the resistance against stress corrosion of such a material.

According to this invention, spreading in the direction of the shock-wave, which can occur on material of larger dimensions, is preferably kept inside the spreading determined by the spherical quadrangle having Miller indices {110} {210} {211} and {553} of the texture direction.

Therefore, in the explosive deformation of sheet material, in which the shock-wave hits the sheet material perpendicularly or substantially perpendicularly to its surface, the present invention involves bringing the material to an anisotropic state having a strongly pronounced texture, prior to the explosive deformation, in which state, the crystallographic surfaces parallel or substantially parallel to the sheet surface have Miller indices lying substantially inside the spherical quadrangle formed by the angle points {110}, {210}, {211} and {553} in the stereographic projection of the unit triangle having the angle points {100}, {110} and {111}.

Such a texture is for instance {110} l12 In a brass with of copper and 30% of zinc this texture can be obtained in different ways.

(1) Cold-rolling to about 50% of cold reduction.

(2) Cold-rolling between 50 and 70% of cold reduction followed by an annealing treatment of from 15 to 30 minutes at a temperature of about 200 C., whereby primary recrystallization is precluded, i.e. stress-free annealing without change of texture.

(3) Cold-rolling above 70% of cold reduction, followed by a heat treatment at a temperature, for example 900 C., which is so high as to give rise to secondary recrystallization. Ths may entail the occurrence of recrystallization twins, but these are essentially stress-free and exert no influence on the stress-corrosion resistance.

-All of these three treatments will lead to the desired texture being obtained, but the stress conditions and the yield point are on different levels.

In a stable austenitic stainless steel, such as steel containing 18% of chrome and more than 8% of nickel, this same texture {110} 112 can be obtained by a similar treatment.

(1) Rolling to about 50% of cold reduction.

('2) Rolling between 50 and 70% of cold reduction followed by a heat treatment between 400 and 600 C. whilst preventing primary recrystallization, i.e, stressree annealing without change of texture.

Rolling with over 70% of cold reduction is impossible with this type of metal, because the temperature at which secondary recrystallization sets in is too high.

Another texture which lies within the range of desired values is {358} 523 An iron-nickel alloy containing over 30% of nickel will develop this texture at a reduction of from 50 to which texture is preserved when later on a heat treatment is applied at temperature of from 600 to 900 C. in order to prevent primary recrystallization. At a reduction of 70% and a temperature of 600 C. this treatment will take from 15 to 30 minutes and at a temperature of 800 C. it need not take longer than from 5 to 10 minutes. However, an increase of reduction requires a decrease in temperature in order to prevent the formation of cubic texture components. Impurities will of course influence the effect of the heat treatment, but a few tests will sufiice for fixing the temperature and the time for reaching the desired effect in the material being treated.

Independently of the fact whether the behaviour of the material is according to the brass or to the copper group, a texture which is of advantage for explosive deformation is always obtained, if the last treatment of the material prior to explosive deformation is a forging treatment with a forging degree of more than about 50%.

A desired texture in sheet material can be obtained by a continuous casting process of the material followed by a forging operation to a degree of more than about 50%.

A single crystal of copper having a diameter of about 10 mm. and a thickness of 5 mm. was explosively deformed with a shock-wave in the direction. The microphotos of this crystal showed no mechanical twins.

I claim:

1. Method for the explosive deformation of a metallic body having a cubically face-centered crystal lattice and a texture, comprising the step of detonating an explosive charge for producing a shock wave directed at least substantially parallel to the 110 direction of the crystal lattice.

2. Method according to claim 1, in which the metallic body is of relatively large dimensions such that spreading in the direction of the shock-wave can occur, wherein said spreading is kept inside the spreading determined by the spherical quadrangle having Miller indices {110}, {210}, {211} and {553} of the texture direction.

3. Method for the explosive deformation of metallic sheet having a cubically face-centered crystal lattice, in which the shock-wave of the explosion hits the sheet material at least substantially perpendicularly, comprising the steps of bringing the metallic sheet into an anisotropic state having a strongly pronounced texture, in which those crystallographic surfaces that are at least substantially parallel to a given sheet surface have Miller indices lying substantially inside the spherical quadrangle formed by the angle points {110}, {210}, {211}, {553} in the stereographic projection of the unit triangle having the angle points {100}, {110} and {111}; and subsequently directing an explosion shock Wave at least substantially perpendicularly to said given sheet surface.

4. A method according to claim 3, wherein said metallic sheet has a {110} 112 texture.

5. A method as defined in claim 3, wherein said metallic sheet has a {358} 523 texture.

6. As an article of manufacture, a metallic object having a face-centered cubic crystal structure and a texture and formed by a process of explosive deformation, the shock wave being directed substantially parallel to the 110 direction of the crystal lattice, said crystal structure being substantially free of mechanical twins, where-by said body has a high corrosion resistance by virtue of the crystal being substantially free of high stress concentrations on the grains and on the grain boundaries.

References Cited by the Examiner UNITED STATES PATENTS 2,703,297 3/ 1955 MacLeod 148-4 3,046,166 7/1962 Hartmann 1481 1.5 3,096,222 7/ 1963 Fielder 14831.55

OTHER REFERENCES Rineh'art: Journal of Applied Physics, vol. 22, 1951, pages l0861087.

DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

R. O. DEAN, Assistant Examiner. 

6. AS AN ARTICLE OF MANUFACTURE, A METALLIC OBJECT HAVING A FACE-CENTERED CUBIC CRYSTAL STRUCTURE AND A TEXTURE AND FORMED BY A PROCESS OF EXPLOSIVE DEFORMATION, THE SHOCK WAVE BEING DIRECTED SUBSTANTIALLY PARALLEL TO THE <110> DIRECTION OF THE CRYSTAL LATTICE,SAID CRYSTAL STRUCTURE BEING SUBSTANTIALLY FREE OF MECHANICAL TWINS, WHEREBY SAID BODY HAS A HIGH CORROSION RESISTANCE BY VIRTUE OF THE CRYSTAL BEING SUBSTANTIALLY FREE OF HIGH STRESS CONCENTRATIONS ON THE GRAINS AND ON THE GRAIN BOUNDARIES. 